Filled dental material based on polymerizable dihydroxy-phenylalanine derivatives

ABSTRACT

Polymerizable dental material which contains (a) at least one radically polymerizable compound according to the general formula I 
                         
(b) initiators for radical polymerization; and (c) filler.

This application claims the benefit of European Patent ApplicationSerial No. 09014467.6, filed Nov. 19, 2009, which is hereby incorporatedby reference in its entirety.

FIELD

The present invention relates to dental materials based on polymerizabledihydroxyphenylalanine derivatives which are suitable in particular ascements, composites and coatings.

BACKGROUND

DE 196 43 007 A1 discloses adhesion promoters and adhesives based onadhesive proteins which are coupled to polymerizable plastic monomers. Apreferred adhesive protein is the Mytilus edulis foot protein isolatedfrom the byssal threads of the common mussel. Adhesion promoters andadhesives are said to be suitable for dental applications.

WO 2006/045034 discloses self-etching dental primers which containdihydroxyphenylalanine (DOPA) combined with dilute mineral acid andoptionally olefinically unsaturated monomers, aldehydes and initiatorsfor light-curing.

U.S. 2006/0009550 discloses the preparation of hydrogels bycopolymerization of aqueous mixtures of poly(ethylene glycol)diacrylateand the radically polymerizable DOPA derivativesN-methacryloyl-3,4-dihydroxy-L-phenylalanine andN-(13-(N′-t-Boc-L-3′,4′-dihydroxyphenylalaninamido)-4,7-10-trioxatridecanyl)-methacrylamide.The hydrogels are said to be suitable as surgical adhesives for medicalor dental application and as carriers for delivering active ingredientsto mucous membranes. It was found that DOPA derivatives exert aninhibiting effect on radical polymerization.

The synthesis of N-methacryloyl-3,4-dihydroxy-L-phenylalanine andN-(13-(N′-t-Boc-L-3′,4′-dihydroxyphenylalaninamido)-4,7-10-trioxatridecanyl)-methacrylamideis described in Lee et al., J. Biomater. Sci. Polymer Edn. 15 (2004)449-464.

L-DOPA is the immediate biological precursor of dopamine(3,4-dihydroxyphenethylamine), a drug for the therapeutic treatment ofParkinson's disease. It is known from DE 100 82 749 T1 thatL-DOPA-containing copolymers of (meth)acrylic acid release the activeingredient L-DOPA in a controlled manner. This is necessarily associatedwith a degradation of the polymers.

Dental materials based on dihydroxyphenylalanine derivatives which aresuitable as cements, composites and coatings are not known from thestate of the art.

SUMMARY

An object of the invention is to provide dental materials which aresuitable as cements, composites and coating materials which arecharacterized by a good adhesion to dentine and tooth enamel, which bondfiller particles in securely and which are characterized by a goodpolymerizability.

The object is achieved according to the invention by dental materials,which

-   -   a) contain at least one radically polymerizable compound        according to the general formula I

in which

-   -   R¹, R² independently of each other are each H or a C₁-C₈ alkyl        residue,    -   R³, R⁴, R⁵ independently of one another are each H or a C₁-C₄        alkyl residue,    -   R⁶ is H, a linear or branched C₁-C₁₀ alkyl residue or a C₁-C₁₀        alkanoyl residue,    -   R⁷ is a linear or branched C₁-C₁₅ alkylene residue or is        dispensed with, wherein the chain of carbon atoms of the alkyl        residue can be interrupted by O or S atoms, is preferably        dispensed with or is a linear or branched C₁-C₁₅ alkylene        residue,    -   X, Y independently of each other are each O or NR⁸ or are        dispensed with,        -   wherein R⁷ can be dispensed with only if X and/or Y are also            dispensed with, and        -   wherein R⁷, X and Y can be dispensed with simultaneously            only if PG¹=H,    -   R⁸ is H or a C₁-C₁₀ alkyl residue,    -   PG¹, PG² independently of each other are each H or a radically        polymerizable group, preferably a vinyl, allyl, (meth)acryl        group, wherein the two residues PG¹ and PG² cannot        simultaneously be H;    -   b) initiators for radical polymerization; and    -   c) filler.

The formula covers only those compounds that conform to the chemicalvalence theory.

The indication that a residue can be interrupted by a heteroatom such asO is to be understood such that the O atoms are inserted into the carbonchain of the residue, i.e. are bordered on both sides by carbon atoms.The number of heteroatoms is therefore at least 1 less than the numberof carbon atoms, and the heteroatoms cannot be terminal.

Preferred meanings for the variables of Formula I are:

-   -   R¹, R² independently of each other each represent H or a C₁-C₃        alkyl residue, preferably H,    -   R³, R⁴ independently of each other each represent H or methyl,        preferably H,    -   R⁵ H or a C₁-C₃ alkyl residue, preferably H,    -   R⁶ H, a linear or branched C₁-C₂ alkyl residue or a C₂ alkanoyl        residue,    -   R⁷ a linear C₁-C₄ alkylene residue or is dispensed with, wherein        the chain of the carbon atoms of the alkyl residue can be        interrupted by O atoms, preferably a C₁₋₄ alkyl residue,    -   X, Y independently of each other each represent O or NR⁸ or are        dispensed with,    -   R⁸ H or C₁-C₂ alkyl residue,    -   PG¹, PG² independently of each other each represent H or a        (meth)acryl group, wherein both residues cannot simultaneously        be H.

Compounds according to Formula I in which PG² is a polymerizable groupand PG¹ is H, and also compounds in which PG¹ and PG² are each apolymerizable group, are particularly preferred.

The preferred meanings of the variables can be chosen independently ofeach other. Compounds in which all variables have one of the preferreddefinitions are particularly preferred.

The materials according to the invention preferably contain 0.05 to 40wt.-%, particularly preferably 1 to 30 wt.-% and quite particularlypreferably 1 to 20 wt.-% of at least one compound according to FormulaI. Unless stated otherwise, all percentages here relate to the totalmass of the dental material.

It was surprisingly found that after curing the materials according tothe invention have a high adhesion not only to collagen but also todental hard tissue such as tooth enamel and dentine and to metallicsubstrates.

It was particularly surprising that the materials are well polymerizableand have good mechanical properties after curing. This was unexpected,as it was known from the state of the art that DOPA derivatives inhibitradical polymerization, which suggested particular problems withmaterials containing fillers, as in this case polymerization isadditionally complicated by the filler. Surprisingly, however, theinhibiting effect of the DOPA was able to be counteracted by theaddition of filler. The filler-containing materials according to theinvention have a higher reactivity than corresponding unfilled materialsand display a much higher polymerizability.

Moreover, it was known from the state of the art that DOPA-containingpolymers can release DOPA, which on the one hand is disadvantageous forthe mechanical stability of the polymers and on the other hand suggestedthe unwanted release of pharmaceutically active substances. However, theactive ingredients according to the invention were stable even afterstorage in water and do not release unwanted components.

Polymerizable dihydroxyphenylalanine derivatives according to thegeneral formula I are known from the state of the art and can beprepared by simple synthesis processes. For example, phenyl-D,L-alaninederivatives (PG¹, PG² and R⁵, R⁶=H; X and R⁷ are dispensed with and Y=O)can be reacted with (meth)acrylic acid chloride (PG²-Cl) to produce acorresponding polymerizable phenylalanine derivative:

SPECIFIC EXAMPLE Synthesis of3,4-dihydroxy-N-methacryloyl-DL-phenylalanine

Phenyl-D,L-alanine derivatives with the substituents R¹, R², R³, R⁴, R⁵and R⁶ can be prepared with known alkylation and acylation methods fromorganic chemistry and in consideration of the protective group technique(cf. T. W. Greene, Protective Groups in Organic Synthesis, J. Wiley &Sons, New York etc. (1980); Hacksell and Högberg, Protective Groups inOrganic Synthesis, Acta Pharm. Suec. 23:323-369 (1986), which are herebyincorporated by reference in their entirety). DOPA derivativessubstituted with R¹ or R² are accessible e.g. by using correspondingsynthesis components during DOPA synthesis. Thus e.g. alkyl-substitutedDOPA derivatives (R¹, R²=alkyl) are accessible by reaction of α-terminalmono- or dialkyl-substituted benzyl bromides with glycine esters ofbenzophenone Schiff's bases analogously to Ooi et al., J. Amer. Chem.Soc. 125:5139 (2003), which is hereby incorporated by reference in itsentirety). The alkylation of the phenolic OH groups (R³ and R⁴) can becarried out according to customary methods, for example by alkylationwith the corresponding alkyl chlorides in the presence of KI analogouslyto Kolasa and Miller, J. Org. Chem. 55:4246 (1990), which is herebyincorporated by reference in its entirety. In this way, an alkylation ofthe amino group (R⁶) can also be achieved. The alkylation of thephenolic OH groups (R³ and R⁴) is also possible with dialkyl sulphatesanalogously to Suarez et al., Synth. Commun. 23:1991 (1993), which ishereby incorporated by reference in its entirety. DOPA derivativesalkylated in α-position (R⁵) are accessible for example via thehydrolysis of correspondingly substituted 2-imidazoline-5-ones analogousto DE 26 58 941 A1.

Preferred examples of polymerizable dihydroxyphenylalanine derivativesof general formula I are:

The polymerizable dihydroxyphenylalanine derivatives according toFormula I are well soluble in organic solvents such as acetone,acetonitrile or ethyl acetate and are thus particularly suitable as aconstituent of hydrophobic composite matrices. They can thereforeadvantageously be combined with radically polymerizable monomers.

The dental materials according to the invention preferably contain mono-and/or polyfunctional (meth)acrylates as radically polymerizablemonomers. By monofunctional monomers are meant monomers with one, bypolyfunctional monomers monomers with more than one, radicallypolymerizable group. Preferred examples are methyl, ethyl, hydroxyethyl,butyl, benzyl, tetrahydrofurfuryl or isobornyl (meth)acrylate,bisphenol-A-di(meth)acrylate, bis-GMA (an addition product ofmethacrylic acid and bisphenol-A-diglycidyl ether), UDMA (an additionproduct of 2-hydroxyethyl methacrylate and 2,2,4-trimethylhexamethylenediisocyanate), di-, tri- or tetraethylene glycol di(meth)acrylate,trimethylolpropane tri(meth)acrylate, pentaerythritoltetra(meth)acrylate as well as glycerol dimethacrylate, 1,4-butanedioldi(meth)acrylate, 1,10-decanediol di(meth)acrylate and 1,12-dodecanedioldi(meth)acrylate.

Hydrolysis-resistant diluting and/or cross-linking monomers canpreferably also be used as additional monomers. Preferred dilutingmonomers are hydrolysis-resistant mono(meth)acrylates, e.g. mesitylmethacrylate, or 2-(alkoxymethyl)acrylic acids, e.g.2-(ethoxymethyl)acrylic acid, 2-(hydroxymethyl)acrylic acid, N-mono- orN-disubstituted acrylamides, such as e.g. N-ethylacrylamide,N,N-dimethacrylamide, N-(2-hydroxyethyl)acrylamide,N-methyl-N-(2-hydroxyethyl)acrylamide, or N-monosubstitutedmethacrylamides, such as e.g. N-ethylmethacrylamide orN-(2-hydroxyethyl)methacrylamide and also in addition N-vinylpyrrolidoneand allyl ether.

Examples of preferred hydrolysis-resistant cross-linking monomers areurethanes of 2-(hydroxymethyl)acrylic acid esters and diisocyanates suchas 2,2,4-trimethylhexamethylene diisocyanate or isophorone diisocyanate,cross-linking pyrrolidones, such as e.g.1,6-bis(3-vinyl-2-pyrrolidonyl)-hexane, or commercially availablebisacrylamides, such as methylene or ethylene bisacrylamide, orbis(meth)acrylamides, such as e.g.N,N′-diethyl-1,3-bis(acrylamido)-propane,1,3-bis(methacrylamido)-propane, 1,4-bis(acrylamido)-butane or1,4-bis(acryloyl)-piperazine which can be synthesized from thecorresponding diamines by reaction with (meth)acrylic acid chloride.

Furthermore, known low-shrinkage radically ring-opening polymerizablemonomers, such as e.g. mono- or multifunctional vinyl cyclopropanes andbicyclic cyclopropane derivatives, preferably those described in DE 19616 183 C2 and EP 03 022 855, or cyclic allyl sulphides, preferably thosedescribed in U.S. Pat. No. 6,043,361 or U.S. Pat. No. 6,344,556, canalso be used as additional monomers. These monomers can alsoadvantageously be used in combination with the di(meth)acrylatecross-linkers listed above.

Preferred ring-opening polymerizable monomers are vinyl cyclopropanes,in particular 1,1-di(ethoxycarbonyl)- or 1,1-di(methoxycarbonyl)-2-vinylcyclopropane or the esters of 1-ethoxycarbonyl- or1-methoxycarbonyl-2-vinyl cyclopropane carboxylic acid with ethyleneglycol, 1,1,1-trimethylolpropane, 1,4-cyclohexanediol or resorcinol.Preferred bicyclic cyclopropane derivatives are2-(bicyclo[3.1.0]hex-1-yl)acrylic acid methyl or ethyl esters or theirdisubstitution products in 3-position, such as(3,3-bis(ethoxycarbonyl)bicyclo[3.1.0]hex-1-yl)acrylic acid methyl orethyl ester. Preferred cyclic allyl sulphides are the addition productsof 2-(hydroxymethyl)-6-methylene-1,4-dithiepane or7-hydroxy-3-methylene-1,5-dithiacyclooctane with2,2,4-trimethylhexamethylene-1,6-diisocyanate or the asymmetrichexamethylene diisocyanate trimers (Desmodur® XP2410 from Bayer AG).

In addition, radically polymerizable polysiloxanes which can be preparedfrom suitable methacryl silanes, such as e.g.3-(methacryloyloxy)propyltrimethoxysilane, can be used as additionalmonomers. The polysiloxanes described in DE 199 03 177 C2 are preferred.

Finally, mixtures of the monomers named above with radicallypolymerizable, acid group containing monomers, so-called adhesionmonomers, can also be used as additional monomers. Preferred acid groupcontaining monomers are polymerizable carboxylic acids such as maleicacid, acrylic acid, methacrylic acid, 2-(hydroxymethyl)acrylic acid,4-(meth)acryloyloxyethyltrimellic acid anhydride,10-methacryloyloxydecylmalonic acid,N-(2-hydroxy-3-methacryloyloxypropyl)-N-phenylglycine and 4-vinylbenzoicacid. Phosphonic acid monomers such as vinylphosphonic acid,4-vinylphenylphosphonic acid, 4-vinylbenzylphosphonic acid,2-methacryloyloxyethylphosphonic acid, 2-methacrylamidoethylphosphonicacid, 4-methacrylamido-4-methyl-pentyl-phosphonic acid,2-[4-(dihydroxyphosphoryl)-2-oxa-butyl]-acrylic acid or2-[4-(dihydroxyphosphoryl)-2-oxa-butyl]-acrylic acid ethyl- or-2,4,6-trimethylphenyl ester are further preferred. Acidic polymerizablephosphoric acid esters, such as 2-methacryloyloxypropyl mono- ordihydrogen phosphate, 2-methacryloyloxyethyl mono- or dihydrogenphosphate, 2-methacryloyloxyethylphenyl hydrogen phosphate,dipentaerythritol-pentamethacryloyloxyphosphate,10-methacryloyloxyde-cyl-dihydrogen phosphate, phosphoric acidmono-(1-acryloyl-piperidine-4-yl)-ester, 6-(methacrylamido)hexyldihydrogen phosphate and1,3-bis-(N-acryloyl-N-propyl-amino)-propan-2-yl-dihydrogen phosphate arealso preferred. Further preferred acid-group-containing monomers arepolymerizable sulphonic acids such as vinylsulphonic acid,4-vinylphenylsulphonic acid or 3-(methacrylamido)propylsulphonic acid.

The dental materials according to the invention preferably do notcontain hydrophilic monomers, such as for example poly(ethylene glycol)di(meth)acrylates, which contribute to an increase in the waterabsorption of the materials and thus adversely affect their usabilityfor dental purposes.

Dental materials which contain as additional radically polymerizablemonomer at least one mono- and/or polyfunctional (meth)acrylate,bis-GMA, UDMA, trimethylolpropane trimethacrylate, glyceroldimethacrylate, 1,10-decanediol dimethacrylate,N,N′-diethyl-1,3-bis(acrylamido)-propane or a mixture thereof areparticularly preferred.

Dental materials which contain as component (d) at least one furtherpolymerizable monomer are preferred. Materials which contain 5 to 90wt.-%, quite particularly preferably 20 to 80 wt.-% of one and/orseveral additional radically polymerizable mono- and/or polyfunctionaldiluting or cross-linking monomers are particularly preferred. Materialswhich also contain 0 to 50 wt.-%, quite particularly preferably 0 to 30wt.-% of one and/or several radically polymerizable acid groupcontaining monomers are further preferred. Materials which contain 5 to80 wt.-% and quite particularly preferably 20 to 70 wt.-% of one orseveral polyfunctional monomers are particularly preferred. Thesepercentages relate to the mass of the monomers in the materials.

Depending on the type of initiator used, the dental material can behot-, cold- or light-polymerizable. Benzophenone, benzoin andderivatives thereof or α-diketones or derivatives thereof, such as9,10-phenanthrenequinone, 1-phenyl-propan-1,2-dione, diacetyl or4,4′-dichlorobenzil are used to initiate radical photopolymerization.Camphorquinone and 2,2-dimethoxy-2-phenyl-acetophenone are preferablyused, and particularly preferably α-diketones combined with amines asreducing agents, such as e.g. 4-(dimethylamino)-benzoic acid esters,N,N-dimethylaminoethyl methacrylate, N,N-dimethyl-sym.-xylidine ortriethanolamine. Norrish type I photoinitiators, above all acyl- orbisacylphosphine oxides, monoacyltrialkyl- or diacyldialkylgermaniumcompounds, such as e.g. benzoyltrimethylgermanium,dibenzoyldiethylgermanium or bis(4-methoxybenzoyl)diethylgermanium arealso particularly preferred. Mixtures of different photoinitiators canalso be used, such as e.g. dibenzoyldiethylgermanium combined withcamphorquinone and 4-dimethylaminoethyl benzoate.

Benzopinacol and 2,2′-dialkylbenzopinacols are particularly suitable asinitiators for hot-curing. Redox-initiator combinations, such as e.g.combinations of benzoyl peroxide with N,N-dimethyl-sym.-xylidine orN,N-dimethyl-p-toluidine, are used as initiators for a polymerizationcarried out at room temperature. In addition, redox systems consistingof peroxides and such reducing agents, such as e.g. ascorbic acid,barbiturates or sulphinic acids, are also particularly suitable.

Materials which contain a photoinitiator, in particular a photoinitiatorbased on camphorquinone/amine, a bisacylphosphine oxide, adiacyldialkylgermanium compound or a mixture thereof are preferredaccording to the invention.

The dental materials according to the invention preferably contain 0.01to 10 wt.-%, preferably 0.1 to 3.0 wt.-% initiator and optionally anactivator.

The compositions used according to the invention furthermore containorganic or inorganic filler particles to improve the mechanicalproperties or to adjust the viscosity. The filler particles preferablyhave an average particle size [determined by transmission (10-80 nm) orscanning electron microscopy (50 nm to 5 μm) or laser diffraction (0.1to 100 μm)] of 10 nm to 50 μm, particularly preferably 10 nm to 30 μmand quite particularly preferably 10 nm to 5 μm.

Preferred inorganic particulate fillers are amorphous sphericalmaterials based on oxides, such as ZrO₂ and TiO₂ or mixed oxides ofSiO₂, ZrO₂ and/or TiO₂ with an average particle size from 10 nm to 1 μm,nanoparticulate or microfine fillers such as pyrogenic silicic acid orprecipitation silicic acid with an average particle size from 10 nm to500 nm and also mini fillers such as quartz, ceramic, glass ceramic orglass powder with an average particle size from 0.1 to 5 μm, preferably0.2 to 3 μm and quite particularly preferably 0.4 to 1.5 μm as well asX-ray-opaque fillers such as ytterbium trifluoride or nanoparticulatetantalum(V) oxide or barium sulphate with an average particle size from10 nm to 500 nm.

The dental materials according to the invention preferably contain 1 to90 wt.-%, preferably 1 to 85 wt.-% and quite preferably 1 to 20 wt.-% or20 to 85 wt.-% filler, wherein the filler content depends on the desiredintended use of the materials. The fillers contribute substantially tothe curing of the materials.

The compositions used according to the invention can optionally containfurther additives, in particular solvents, such as acetone, ethylacetate and mixtures thereof, as well as stabilizers, flavourings, dyes,microbiocidal active ingredients, fluoride-ion-releasing additives,optical brighteners, plasticizers or UV absorbers. The dental materialsaccording to the invention preferably contain no water, i.e. 0.5 wt.-%water at most.

According to a further preferred embodiment, the materials according tothe invention contain boric acid, preferably in a quantity from 0 to 2.0mol equivalent relative to the compound according to Formula I,particularly preferably 0 to 1.0 mol equivalent. It was found that boricacid, in particular in the case of R³=R⁴=H, reduces the inhibitingeffect of DOPA derivatives on radical polymerization. Therefore whenboric acid is used the addition of filler can be dispensed with, whereinmaterials which contain filler and boric acid are preferred.

Compositions which contain as component (e) 0 to 95 wt.-%, particularlypreferably 0 to 70 wt.-% and quite particularly preferably 5 to 50 wt.-%non-aqueous solvent are particularly suitable according to theinvention.

The dental materials according to the invention preferably contain:

-   -   a) 0.05 to 40.0 wt. %, preferably 1 to 30 wt. % and particularly        preferably 1 to 20 wt. % of at least one compound according to        Formula I;    -   b) 0.01 to 10 wt. %, preferably 0.1 to 3.0 wt. % initiator;    -   c) 1 to 85 wt. %, preferably 1 to 20 wt. % (for use as coating        material) or 20 to 85 wt. % (for use as cement or composite)        filler;    -   d) 0 to 90 wt. %, preferably 0 to 80% wt. % and particularly        preferably 5 to 80 wt. % of at least one additional monomer;    -   e) 0 to 95 wt. %, preferably 0 to 70 wt. % and particularly        preferably 5 to 50 wt. % solvent.

The dental materials according to the invention are particularlysuitable as cements, composite materials, filling materials, adhesivesand as coating materials.

The invention is explained in more detail below by means of examples.

EMBODIMENT EXAMPLES Example 1 Synthesis of Polymerizable3,4-Dihydroxy-DL-Phenylalanines (DL-DOPA)

General Procedure for the N-acylation of DL-DOPA:

A mixture of 19.72 g (0.10 mol) DL-DOPA, 64.56 g (0.40 mol)hexamethyldisilazane and 4.00 ml trimethylchlorosilane was stirred for 3h at 120° C. bath temperature. Volatile constituents were then removedat 70° C./20 mbar. 50 ml xylene was added to the residue and the mixturere-concentrated (70° C./20 mbar). The thus-obtained intermediate stagewas dissolved in 200 ml methylene chloride, a solution of 0.10 mol acidchloride in 20 ml methylene chloride added to it at −70° C. and themixture stirred accompanied by slow heating to room temperature for 2 d.After concentration in vacuum (40° C./600 mbar) 500 ml tert-butanol and100 ml water were added to the residue, the mixture stirred for 30 minat room temperature, dried with sodium sulphate, filtered and thesolvent distilled off (40° C./20 mbar). For purification, the rawproduct was heated under reflux in 250 ml ethyl acetate for 1 h andfiltered off from the undissolved material. The clear, yellow filtratewas desolventized (40° C./180 mbar) and then dried at 0.1 mbar to aconstant weight.

a) 3,4-dihydroxy-N-methacryloyl-DL-phenylalanine (MADOPA)

MADOPA was obtained using methacrylic acid chloride. Yield: 14.8 g(56%), yellowish solid (m.p.: 63-65° C.). Purity (HPLC): 96.16%

¹H-NMR (400 MHz, DMSO-d₆): δ=1.79 (s, 3H, CH₃), 2.76-2.92 (m, 2H, CH₂),4.30-4.36 (m, 1H, NCH), 5.31, 5.62 (2 s, each 1H, ═CH₂), 6.47, 6.58,6.60-6.61 (dd, J=8 Hz, 2 Hz, 1H; s, 1H; m, 1H, ═CH—), 7.93 (d, J=8 Hz,1H, NH), 8.71 (br. s, 2H, OH), 12.5 (br. s, 1H, COOH).

¹³C-NMR (100 MHz, DMSO-d₆): δ=18.5 (CH₃), 35.7 (CH₂), 54.1 (NCH), 115.2,116.4, 119.8 (═CH_(aromatic)), 119.5 (C═CH₂), 128.7, (═C_(aromatic)),139.4 (C═CH₂), 143.7, 144.8 (HO—C═), 167.5 (CONH), 173.2 (COOH).

IR (diamond ATR): ν=3202 (br, m, N—H, O—H), 2933 (m, CH₂, CH₃), 1717 (s,C═O_(acid)), 1652 (s, C═O_(amide)), 1604 (s, C═C), 1532 (s, N—H), 1444(s, aromatic), 1422 (s, CH₂, CH₃), 1372 (m, CH₃), 1194 (s, C—OH), 1116(s, C—N), 873 cm⁻¹ (s, ═CH).

b) N-acryloyl-3,4-dihydroxy-DL-phenylalanine (ADOPA)

ADOPA was obtained using acrylic acid chloride. Yield: 14.8 g (56%),yellowish solid (m.p.: 143-145° C.). Purity (HPLC): 95.84%.

¹H-NMR (400 MHz, DMSO-d₆): δ=2.69-2.92 (m, 2H, CH₂), 4.39-4.44 (m, 1H,NCH), 5.57-5.60, 6.04-6.08, 6.26-6.32 (3 m, each 1H, HC═CH₂), 6.47, 6.61(d, J=8 Hz, 1H; s, 2H, ═CH_(aromatic)), 8.35 (d, J=8 Hz, 1H, NH), 8.70,8.74 (2 br. s, each 1H, OH), 12.7 (br. s, 1H, COOH).

¹³C-NMR (100 MHz, DMSO-d₆): δ=36.2 (CH₂), 53.8 (NCH), 115.3, 116.3,119.7 (═CH_(aromatic)), 125.6 (HC═CH₂), 128.2, (═C_(aromatic)), 131.3(HC═CH₂), 143.8, 144.9 (HO—C═), 164.4 (CONH), 173.0 (COOH).

IR (diamond ATR): ν=3300 (br, m, N—H, O—H), 2920 (m, CH₂), 1717 (s,C═O_(acid)), 1653 (s, C═O_(amide)), 1601 (s, C═C), 1516 (ss, N—H), 1444(s, aromatic), 1414 (s, CH₂), 1191 (s, C—OH), 1114 (s, C—N), 969 (s,═CH), 871 cm⁻¹ (s, ═CH).

Example 2 Radical Homopolymerization of MADOPA in Solution

The monomer MADOPA (2.0 mol/l) was polymerized in DMF with2,2′-azobisisobutyronitrile (AIBN, 2.0 mol %) at 65° C. After 5 h thepolymerization was stopped and the polymerisate precipitated out of tentimes the quantity of diethyl ether, filtered off and dried to constantweight in fine vacuum at 50° C. A white polymer was obtained invirtually quantitative yield. The polymer structure was able to beconfirmed by means of ¹H-NMR spectroscopy.

NMR spectroscopy data for poly(MADOPA):

¹H-NMR (400 MHz, MeOD, δ in ppm): 0.88 (H_(a), H_(b), 5H), 2.6-3.1(H_(g), 2H), 4.57 (H_(e), 1H), 6.75 (H_(i), H_(j), H_(k), 3H), 8.0(H_(NH), 1H)

¹³C-NMR (100 MHz, MeOD, δ in ppm): 19.4 C_(b), 37.9 C_(g), 46.8 C_(c),48.9 C_(e), 56.2 C_(a), 117.7 C_(j/k), 122.3 C_(i), 129.9 C_(h), 145.2C_(l), 146.2 C_(m), 175.1 C_(f), 178.9 C_(d)

Example 3 Radical Copolymerization of ADOPA with MMA in Solution

The monomer ADOPA (0.2 mol/l) and methyl methacrylate (MMA) (1.8 mol/l)were polymerized in DMF with 2,2′-azobisisobutyronitrile (AIBN, 2.0 mol%) at 65° C. After 5 h the polymerization was stopped and thepolymerisate precipitated out of ten times the quantity of methanol,filtered off and dried to constant weight in fine vacuum. A whitepolymer was obtained in virtually quantitative yield. The polymerstructure was able to be confirmed by means of ¹H-NMR spectroscopy. Acopolymer structure with 18 mol % ADOPA units resulted.

Example 4 Preparation of Composite Cements Based on MADOPA

According to Table 1 given below, composite fixing cements based on adimethacrylate mixture were prepared with the polymerizable DOPAderivative MADOPA (cement A) and the monofunctional benzyl methacrylate(cement B, comparison example) and alsobis-(4-methoxybenzoyl)diethylgermanium as photoinitiator by means of an“Exakt” roll mill (Exakt Apparatebau, Norderstedt). Testpieces (rodswith a length of 25 mm and a square cross-section of 2 mm×2 mm) wereprepared from the materials which were irradiated twice for 3 minuteswith a dental light source (Spectramat®, Ivoclar Vivadent AG) and cured.The bending strength and the bending E modulus were determined accordingto ISO standard ISO 4049 (Dentistry—Polymer-based filling, restorativeand luting materials). The results are summarized in Table 2.

The example shows that filled DOPA-monomer-containing formulations leadto composite cements with good mechanical properties, while analogousunfilled resins do not produce usable materials.

TABLE 1 Composition of the composite cements Cement A Resin A*⁾ CementB*⁾ Component [wt.-%] [wt.-%] [wt.-%] Bis(4- 0.58 1.45 0.58methoxybenzoyl)diethylgermanium UDMA¹⁾ 27.64 69.10 27.64 Triethyleneglycol 7.81 19.53 7.81 dimethacrylate MADOPA (Ex. 1a) 3.90 9.92 — Benzylmethacrylate — — 3.90 Pyrogenic silicic acid²⁾ 41.34 — 41.34 Ytterbiumtrifluoride 18.73 — 18.73 (Rhone-Poulenc) *⁾Comparison ¹⁾Additionproduct of 2 mol 2-hydroxyethyl methacrylate and 1 mol2,2,4-trimethylhexamethylene diisocyanate ²⁾Aerosil OX-50 (Degussa)

TABLE 2 Mechanical properties of the composite cements Property Cement AResin A*⁾ Cement B*⁾ Bending strength (MPa) 114 32 109 after 24 h WI¹⁾Elastic modulus (MPa) 5280 600 5200 after 24 h WI¹⁾ *⁾Comparison ¹⁾WI =water immersion of the testpieces at 37° C.

Example 5 Preparation of a Composite Based on MADOPA

Dental composites with the composition given in Table 3 were preparedusing a Linden kneader. The mechanical properties were examinedanalogously to Example 4 and are summarized in Table 4.

TABLE 3 Composition of the composites Composite C Composite D*⁾Component [wt-%] [wt.-%] Bis(4-methoxybenzoyl)diethylgermanium 0.22 0.22UDMA¹⁾ 6.72 6.72 Triethylene glycol dimethacrylate 1.77 6.72 MADOPA 1.81— Benzyl methacrylate — 1.81 Ytterbium trifluoride (Rhone-Poulenc) 14.8914.89 Spherosil, silanized (Tokoyama Soda)²⁾ 14.39 14.39 Glass fillerGM27884 (Schott)³⁾ 51.61 51.61 Aerosil OX-50 (Degussa) 1.00 1.00*⁾Comparison ¹⁾Addition product of 2 mol 2-hydroxyethyl methacrylate and1 mol 2,2,4-trimethylhexamethylene diisocyanate ²⁾SiO₂—ZrO₂ mixed oxide(average primary particle size: 250 nm) ³⁾Silanized Ba—Al-boron silicateglass filler with an average particle size of 1.5 μm

TABLE 4 Mechanical properties of the composites Property Composite CComposite D*⁾ Bending strength (MPa) after 24 h WI¹⁾ 158 195 Elasticmodulus (MPa) after 24 h WI¹⁾ 15000 16200 *⁾Comparison ¹⁾WI = waterimmersion of the testpieces at 37° C.

It should be mentioned that any references, including patents, patentapplications and published articles that are cited herein areincorporated by reference in their entirety. Any word used herein inplural form may also include singular forms of the word and any wordused in singular form herein may also include plural forms of the word.

Although the present invention has been described in connection withpreferred embodiments thereof, it will be appreciated by those skilledin the art that additions, deletions, modifications, and substitutionsnot specifically described may be made without department from thespirit and scope of the invention as defined in the appended claims.

What is claimed:
 1. Polymerizable dental material, which comprises a) atleast one radically polymerizable compound according to the generalformula I

in which R¹, R² are each H, R³, R⁴, R⁵ are each H, R⁶ is H, a linear orbranched C₁-C₂ alkyl residue or a C₂ alkanoyl residue, R⁷ is a linearC₁-C₄ alkylene residue, X, Y independently of each other are each O orNR⁸ or are dispensed with, R⁸ is H or a C₁-C₂ alkyl residue, PG¹, PG²independently of each other are each H or a (methy)acryl group, whereinboth residues PG¹ and PG² cannot simultaneously be H; b) an initiatorfor radical polymerization; and c) a filler.
 2. Dental materialaccording to claim 1, which further comprises at least one of d) anadditional polymerizable monomer and e) a solvent.
 3. Dental materialaccording to claim 1, which comprises a) 0.05 to 40 wt.-% of at leastone compound according to Formula I; b) 0.01 to 10 wt.-% initiator; c) 1to 85 wt.-% filler; d) 0 to 90 wt.-% of at least one additional monomer;and e) 0 to 95 wt.-% solvent.
 4. Dental material according to claim 2,wherein the additional polymerizable monomer comprises at least onemono- and/or polyfunctional (meth)acrylate.
 5. Dental material accordingto claim 2, which is free of hydrophilic monomers.
 6. Dental materialaccording to claim 1, wherein the filler has an average particle sizefrom 10 nm to 50 μm.
 7. Dental material according to claim 1, whereinthe filler comprises amorphous spherical materials based on oxides ormixed oxides with an average particle size from 10 nm to 1 μm, and/ornanoparticulate or microfine fillers with an average particle size from10 nm to 500 nm, and/or mini fillers with an average particle size from0.1 to 5 μm, and/or X-ray-opaque fillers with an average particle sizefrom 10 nm to 500 nm.
 8. Dental material according to claim 1, whichcontains 0.5 wt.-% water at most.
 9. Dental material according to claim1, which contains boric acid in a quantity from 0 to 2.0 mol equivalentrelative to the compound according to Formula I.
 10. Dental materialaccording to claim 3 for use as a coating material, which comprises a) 1to 30 wt.-% of at least one compound according to Formula I; b) 0.1 to3.0 wt.-% initiator; c) 1 to 20 wt.-% filler; d) 0 to 80 wt.-% of atleast one additional monomer; and e) 0 to 70 wt.-% solvent.
 11. Dentalmaterial according to claim 3 for use as a cement or composite, whichcomprises a) 1 to 30 wt.-% of at least one compound according to FormulaI; b) 0.1 to 3.0 wt.-% initiator; c) 20 to 85 wt.-% filler; d) 0 to 80wt.-% of at least one additional monomer; and e) 0 to 70 wt.-% solvent.12. Dental material according to claim 6, wherein the filler comprisesan average particle size from 10 nm to 30 μm.
 13. Dental materialaccording to claim 6, wherein the filler comprises an average particlesize from 10 nm to 5 μm.
 14. Dental material according to claim 9,wherein the boric acid quantity is 0 to 1.0 mol equivalent.
 15. Dentalmaterial according to claim 2, wherein the additional polymerizablemonomer comprises at least one N-monosubstituted acrylamide and/or atleast one N-disubstituted acrylamide and/or at least oneN-monosubstituted methacrylamide.
 16. A dental cement, compositematerial, filling material, adhesive or coating material, comprising thedental material of claim
 1. 17. Dental material according to claim 3,which comprises d) 5 to 90 wt.-% of at least one additional monomer. 18.Dental material according to claim 17, which comprises d) 5 to 80 wt.-%of at least one additional monomer.
 19. Dental material according toclaim 3, which comprises e) 0 to 70 wt.-% solvent.
 20. Dental materialaccording to claim 19, which comprises e) 0 to 50 wt.-% solvent.